A particularly effective integrated circuit package is achieved by multilayer ceramic (MLC) technology. In general, the package is comprised of a plurality of layers of ceramic material which are laminated together and subsequently fired to sinter the layers into a unitary ceramic "brick". Upon a top surface of the brick are mounted one or more integrated circuit die. The opposite surface of the brick is provided with a plurality of protruding electrical terminals for coupling the package to, for example, an electronic circuit board.
Typically, each of the layers is first provided in a "greensheet" form, that is, as an unfired polymer binder which may have a desired quantity of ground glass material distributed throughout. Holes are made through the layers, typically by a punching process; each hole defining the desired location of a conductive via. The holes are thereafter filled with a paste which comprises conductive metal particles, such as molybdenum. If desired, conductive pathways may also be formed between some of the vias by applying the metallic paste in a desired configuration by well known screening operations. A plurality of greensheets are thereafter laminated together to form a multilayered structure. Some of the vias of adjacent greensheet layers are typically formed in registration with one another for producing continuous vias which extend from one surface of the structure to the opposite surface.
After forming the multilayer structure in the manner described above the structure is baked by a, typically, two step process. During a first step the structure is baked at a first temperature such that any organic material within the structure is burned away. Thereafter, the structure is baked at a second, higher temperature such that the laminated greensheet layers are sintered into a multilayered ceramic brick. During this baking process the metal paste is cured such that solid metallic interconnections are formed through the via holes and between selected vias. One or more integrated circuit die are then typically bonded to a top surface of the brick. The opposite, bottom surface of the brick is thereafter provided with protruding electrical conductors for subsequently coupling the resulting ceramic package, or module, to a carrier such as a printed circuit board.
Conventional methods of providing the protruding electrical conductors involve a brazing operation whereby electrically conductive pins or studs are brazed to pads electrically connected to the vias which have an end which extends to a surface of the module. This subsequent brazing operation has been found to be costly. Also, due to the required physical joining of the pin to the via end surface, such a pin brazing technique may introduce a mechanical reliability problem.
It is therefore one object of the invention to provide a multilayered ceramic body having one or more conductors disposed within, certain of the conductors having an integral end portion protruding in an upstanding manner above a surface of the body.
It is another object of the invention to provide a method of forming metallic pins or studs upon a surface of a ceramic structure.
It is a further object of the invention to provide a method of forming metallic pins or studs upon the bottom surface of a ceramic integrated circuit module which eliminates the conventional method of brazing the pins or studs to exposed ends of metallic vias.
It is a still further object of the invention to provide a method of forming metallic pins or studs upon the bottom surface a ceramic integrated circuit module by abrading the bottom surface selectively such that terminal portions of metallic vias are left exposed in a protruding, upstanding fashion above the bottom surface.
It is one still further object of the invention to provide a method of forming metallic pins or studs upon a surface of a ceramic integrated circuit module by abrading the surface selectively such that terminal portions of metallic vias are left exposed in a protruding fashion above the surface, the surface being abraded by a stream of abrasive particles which are directed against the surface.
Another object of the invention to provide a method of forming metallic pins or studs upon a surface of a ceramic integrated circuit module by abrading the surface selectively such that terminal portions of metallic vias are left exposed in a protruding fashion above the surface, the surface being abraded by a stream of abrasive particles which are directed against the surface, the surface being rotated beneath a grit blasting nozzle which is linearly translated above the surface.